An expert told a federal judge in Nashville on Monday that a Gallatin power plant released more coal ash pollutants in an eight-year period than the 2008 in coal ash spill in Kingston and the 2010 Deepwater Horizon oil spill in the Gulf of Mexico.

TVA said it fixed the problem decades ago by repairing underground sinkholes. Groves testified that was "improbable."

In the current trial, U.S. District Judge Waverly Crenshaw will decide whether the utility is liable. Through expert testimony, the trial will delve into details of the movement of groundwater, as well as analyses of pollutants in one of Tennessee's sources of drinking water.

The environmental groups want the judge to order TVA to pay per at least $37,000 per violation of the Clean Water Act, per day of violation, and order excavation of coal ash to move it to lined, dry storage, according to court records.

TVA argued there was no violation of federal law and they were obeying the state permit. Lawyer David Ayliffe, defending TVA, said the environmental groups cannot prove a direct tie between contaminants in the water and the coal ash ponds. TVA said it cannot be held responsible for violations outside the Clean Water Act's five-year statute of limitations (which would bar the releases in the 1970s).

The plant burns an average of 13,000 tons of coal each day and generates power for the equivalent of 300,000 homes. Coal ash, a byproduct, contains arsenic, selenium, mercury and other pollutants — all harmful to people and wildlife when found in high concentrations.

The utility, which powers 9 million customers in parts of seven Southern states, is making a $1.2 billion investment at the Gallatin Fossil Plant to reduce air pollution and begin storing coal ash in safer ways. The environmental groups say it is not enough.

A map of the Gallatin Fossil Plant on the Cumberland River and sites of seeps was produced as part of the pending lawsuit against TVA.(Photo: Public court filing)

The unlined storage ponds at the Gallatin site sit above limestone riddled with sinkholes that allowed the coal ash to seep into groundwater and into the Cumberland River, the environmental groups say. They say the utility knew the condition of the limestone would allow contaminated water to run through.